As documented in the excellent Enterprise Flash Drive Cost and Technology Projections overview here on Wikibon, the two most popular justifications for deploying Solid State Storage solutions are (1) to reduce operational "green" costs, and (2) to improve I/O response times.

However, both of these justification scenarios de-emphasize overall capacity, while the first also assumes short-stroking limitations cannot be overcome with multi-tenancy wide-striped LUN's using thin provisioning technology.

The advent of primary storage deduplication now offers an enticing third justification scenario which builds nicely on the first two, without sacrificing capacity. Imagine a "mirror asymptote" overlaid on top of this diagram but descending from the opposite side. That asymptote would use the same scale but reflect the dedupe ratios of popular enterprise data sets. For example, 10:1 is common for virtual desktops, 5:1 for virtual servers, 3:1 for scientific data and data warehouses and so on.

Therefore the intersection point between the asymptotes represents where deduped flash becomes lower cost than the equivalent capacity of primary disk that is not deduped.

Action Item: Now more than ever, it's time to examine your primary Tier 1 data sets for "de-dupability". The cost-neutral opportunity to transparently reduce the OpEx of your most expensive tier of storage while simultaneously improving I/O response times by an order of magnitude is manna from infrastructure heaven.

Comments on 'Flash at the price of Disk'

Is comparing the cost of deduped flash to un-deduped disk an apples to apples comparison, however? If the savings is in the deduping, then how does moving to flash save over staying on the disk and just deduping there?
I think one issue that is not discussed is comparitive operating lives. Disks age whenever they spin, which in most cases means whenever they are powered up, regardless of whether data is being accessed or not. Flash only ages when data is written or read. This means that flash that holds data that is not often read or changed (for instance backups of sectors) can last a very long time.
Also disks tend to fail catastrophically when the bearings on which they ride fail. Flash usually fails gradually, sector by sector. As a result, while disks often require "hot" backup for instant failover, flash may not as sectors can be duplicated on the same device. And flash gives you warning before you have to replace the entire device, so you do not have to have a replacement ready to go sitting idle.
So how do this differences change the price ratio between flash and disk?